1. Field of the Invention
The present invention relates to a sealing structure and an organic electroluminescence device.
2. Description of the Related Art
Research and development have been extensively conducted on organic electroluminescence elements. In the fundamental structure of the organic electroluminescence element, a layer containing a light-emitting organic compound is interposed between a pair of electrodes. By applying voltage to this element, light emission from the light-emitting organic compound can be obtained.
The light-emitting device using an organic electroluminescence element is, for example, a lighting device, or an image display device including a thin film transistor. The organic electroluminescence element can be formed in a film shape and thus easily increased in area, which allows a lighting device with a planar light source to be realized. In addition, an image display device using an organic electroluminescence element needs no backlight which is necessary for liquid crystal display devices and the like; therefore, thin, lightweight, high contrast, and low power consumption display devices can be obtained.
It is known that when the organic electroluminescence element is exposed to the air (including moisture, oxygen, and the like), its performance degrades rapidly. It is thus required that the organic electroluminescence element be hermitically sealed with a material having a high gas barrier property so as not to be exposed to the air.
A sealing technique using glass frit including a low-melting-point glass is known as a technique that realizes sealing with a high gas barrier property. The technique disclosed in Patent Document 1 is as follows: a paste containing a binder and a frit material including a low-melting-point glass is applied onto a glass substrate; the binder is removed through prebaking; and the glass frit is irradiated with laser light while a counter glass substrate is provided over the glass substrate, whereby the glass frit is melted and the substrates are bonded to each other and sealed with the glass frit. When a device using an organic electroluminescence element is sealed with such glass frit, the organic electroluminescence element can be isolated from the external air and a light-emitting device with high reliability can be realized.
In a light-emitting device to which an organic electroluminescence element is applied, there are common power supply lines between a substrate and glass frit and the number of common power supply lines overlapping the glass frit varies depending on the location. For example, there is a plurality of common power supply lines between the glass frit and the substrate at an edge portion of one side of a sealing structure and there is one common power supply line between the glass frit and the substrate at the middle portion of the one side of the sealing structure. When the glass frit is irradiated with laser light, the laser light is absorbed or reflected by the common power supply lines. Therefore, in the case where the degree of overlap between the common power supply lines and the glass frit varies depending on the location, there is a problem in that a difference is generated in the temperature distribution of the glass frit and the glass frit cannot be sufficiently melted; thus, a sealing structure with high air-tightness and an organic electroluminescence device with high air-tightness cannot be manufactured.